Field of the Invention
Recently, a metallic magnetic powder for high recording density has been used instead of .gamma.-Fe.sub.2 O.sub.3, Fe.sub.3 O.sub.4 and cobalt-adsorbed .gamma.-Fe.sub.2 O.sub.3 which have been used in an audio cassette tape whereby electromagnetic characteristics (sensitivity and MOL) in high frequency region have been remarkably improved. The metallic magnetic powder which is used in practice, usually has a coercive force of about 1100 Oe. In an audio cassette, the metallic magnetic powder having the standard coercive force has been usually used. The standard coercive force is considered in view of magnetic characteristics (squareness ratio and orientation) of the metallic magnetic powder and a magnetic head of a recording device. The standard coercive force is about twice of the coercive forces of the chromium type magnetic powder and cobalt-adsorbed magnetic powder which have been used. Therefore, the characteristics in high frequency region are excellent, however, the characteristics in low frequency region especially maximum output level (MOL) are inferior. Thus, the advantage of high maximum output level in high frequency region is not so effective. When the maximum output level is high, the input level in the recording can be improved whereby excellent S/N can be imparted in the recording. However, when the maximum output level in low frequency region is low even though the maximum output level in high frequency region is high, the low frequency component is distorted by increasing the input in the recording, though the high frequency component of the original sound can be recorded at excellent S/N. It could not increase the input level in the recording to be so high if a low distortion in the whole frequency regions is required in the recording. Therefore, in the conventional magnetic recording medium using the metallic magnetic powder, the maximum output level in high frequency region could not effectively utilized.
It has been known that a magnetic recording medium having double magnetic layers using a magnetic powder having high coercive force in an upper layer and a magnetic powder having low coercive force imparts high electromagnetic characteristics. However, the conventional a two magnetic layer type recording tape has disadvantages of high distortion in middle frequency region and high output fluctuation.